JPS6021205B2 - How to dissolve reduced iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves melting reduced iron in an electric induction furnace as a part of the raw material for smelting iron, and then adding additives for adjusting the composition such as ferrosilicoso and ferromanganese and reducing iron itself. This is an efficient method that aims to improve the melting process of raw materials for smelting and other cast iron, promote the reduction reaction of iron oxide in the generated slag, and suppress the amount of lining erosion caused by slag to the lowest possible level. It concerns a method of dissolution.

If iron ore is reduced at a relatively low temperature that does not cause softening or melting, the iron oxide in the iron ore becomes metallic iron and reduced iron is obtained.

The gangue in the ore remains in this reduced iron, but there are few impurities in the reduced metal iron that are caused by the vein or the reducing agent.The quality varies depending on the manufacturing method, etc. All iron 80
It has a reduction rate of ~95%, metallic iron 70-93%, and a total reduction rate (metallic iron/total iron) of approximately ~96%, and has great potential to be used as a raw material for steel manufacturing and mirror iron melting. However, as mentioned above, the gangue in the ore remains in the reduced iron, and if this reduced iron is melted, a large amount of slag will be generated, which will cover the surface of the moat. The raw materials for melting are suspended on this slag, or
In addition, the material becomes entangled, which significantly lengthens the dissolution time, resulting in a decrease in dissolution efficiency and a decrease in the melting yield of raw materials.

Further, since these slags are kept in the furnace for a long time, they tend to erode the line slag of the electric furnace, resulting in a problem that the service life of the slag is significantly shortened. Conventionally, arc furnaces and cupolas were often used to melt reduced iron, but these are relatively easy to deal with the problems mentioned above, such as making it possible to repair the lining of the melting furnace during operation. It's for a reason.

However, in recent years, Kangai-type low-frequency induction furnaces have become widely used as melting furnaces for cast iron, but in order to repair the lining of the melting furnace, it is necessary to stop the melting furnace and restart the melting furnace. All of the molten metal must be extracted before the process, and solving the above-mentioned problems has become a major challenge. One of the advantages of electric transfer furnaces is their large diameter, which makes it possible to bag large quantities of balers made by forming steel scrap into large rectangular parallelepipeds using a press.

When using this steel scrap as a material for melting, additives such as graphite as a recarburizer, ferrosilicon, and ferromanganese are required to adjust the composition, but the dissolution process of these additives is Naturally, this is also affected by the slag, and is also greatly influenced by the order in which reduced iron and these additives are charged. This is because reduced iron is very porous and contains a large amount of air in its pores, and the Q in this air oxidizes Si, Mn, C, etc. in the molten metal, and on the other hand, the iron oxide in the reduced iron In the process of dissolving into the molten metal, it is reduced by Si, Mn, C, etc. in the molten metal, and all of them become S.
i, Mn, C, etc. are consumed. Si, Mn. Among the elements such as C, the elements that mainly participate in these redox reactions are controlled by the relationship between the temperature at the part where reduced iron dissolves in the port edge and the reaction proceeds and the equilibrium concentration in the melt. here,
If ferrosilicon/ferromanganese is charged before charging reduced iron, the concentration of Si and Mm in the source water will increase, and when reduced iron is added there, the above-mentioned redox reaction will occur mainly due to Si and Mn. As a result, Si and Mn are consumed, and the dissolution rate of ferrosilicon and ferromanganese is significantly reduced.

In view of the above-mentioned circumstances of the existence of reduced iron, etc., the present invention has been developed to provide melting materials such as reduced iron, ferrosilicon, ferromanganese, etc.
An effective melting method was found by considering the timing of charging additives for adjusting the composition, such as recarburizing materials, and was completed. First, materials to be used as raw materials for cast iron such as iron raw materials such as steel scrap and return material and recarburizing materials for composition adjustment are placed in bags, and after these materials have melted down, reduced iron is poured into the bag.
This method is characterized in that after removing the slag generated by dissolving reduced iron, additives for adjusting the composition such as ferrosilicon and ferromanganese are charged.

In order to bag iron raw materials such as recarburizer and steel scrap return material before bagging reduced iron, the dissolution rate of C and iron raw materials can be increased without being hindered by slag caused after reduction. , the dissolution rate can also be increased. Therefore, in order to inject reduced iron into a melt wound where the C concentration is high, the oxygen and iron oxide brought by the reduced iron undergo a reduction reaction mainly with C, and Si and Mn participate in the reaction only in an auxiliary manner. It doesn't matter. For this reason, iron oxide can be efficiently reduced, and the effect of reducing the amount of slag generated can also be expected. In addition, since reduced iron is injected after steel scrap, etc. is injected, there is a large amount of molten metal when the reduced iron melts down (because the molten metal surface is at a high position, slag off can be easily performed, and slag is generated). At the same time, since the slag is slag-off, the slag generated from the reduced iron is not retained in the furnace for a long time, so there is an advantage that the amount of corrosion of the lining is extremely small. Then, the slag is removed, and additives for adjusting the composition such as ferrosilicon and fluoromanganese are charged at the end after the reduction reaction mainly due to C has finished, so that Si, Mh' and other components are not consumed in large quantities in the reduction reaction, and the slag is removed. These additives also maintain a high dissolution rate because they are not entrained in water. The present invention will be explained below using examples.

(Example) Using a low frequency induction furnace with a melting capacity of 1.5 tons, raw materials for melting were charged and melted in the following composition and order.

○｝Cupola source water equivalent to FC2 500k9 charged '21
Charge steel scrap 250k9 sword o carbon material 19k9.

It melted when the furnace power was 320KW for 20 minutes.
'3' Charge 500k9 of return material.

The furnace power was 36 W, melting occurred in 35 minutes, and the temperature was increased to 1400 qo in 45 minutes. ■ Reduced iron 250k9 hishi type.

Melting takes place in 18 minutes using a furnace power of 350-400KW. At this time, it was observed that the reduced iron was rapidly dissolved without being entangled in the slag. Immediately after the reduced iron melting was completed, the slag was removed. Side: Packed with 14k9 of ferrosilicone and 5.4k9 of ferromanganese.

After heating for 30 minutes with a furnace body power of 400 KW, it was drained at 1500°C. The results of operation under the above conditions are shown in Table 1.

(Comparative Example 1) The same materials as in the example were used in the same amounts, but only the order of addition was changed as follows.

{1' Cupola source water '21 Steel scrap Juka carbon material + ferrosilicon + ferromanganese '3' Reduced iron [4- Returning material Table 1 shows the operation results under the above conditions.

(Comparative example 2) The order of addition was further changed as follows.

m Cupola source water ■ Steel scrap '3' Reduced iron (4' Ferromanganese + ferro silicon decacharide material ■ Reconstitution material Table 1 As can be seen from the table, examples in which the order of addition is the same as described in the claims column are Compared to Comparative Examples 1 and 2, first, the dissolution steps of ferrosilicon and ferromanganese were greatly improved.

Furthermore, compared to Comparative Example 2, the reduction rate of iron oxide in the slag was higher and the amount of slag generated was smaller. Also, compared to Comparative Example 1, the iron oxide reduction rate is almost the same, but the amount of slag generated is smaller due to the slight erosion of the lining. From these facts, it is understood that the dissolution method according to the present invention is very efficient.

Claims (1)

[Claims] 1. When reducing iron is melted in an electric induction furnace as part of raw materials for cast iron smelting, iron raw materials such as steel scrap and return material are first added to the electric induction furnace in which a predetermined amount of raw hot water is stored. A charge to be used as a raw material for cast iron, such as a recarburizer for composition adjustment, is charged, and then, after the charge has melted down, the reduced iron is charged, and then, after the generated slag is removed, A method for melting reduced iron, characterized by charging additives for composition adjustment such as ferrosilicon and ferromanganese.